The female witness said Mr Shephard was walking alone along the track carrying a box of beer.
His body was found a week later in Tauranga Harbour and police are appealing for more witness to come forward.
Detective Sergeant Iain Chapman said: "The woman who reported this was concerned about wasting our time with information that may not be relevant but having read a recent renewed appeal made contact with us.
"It just goes to show that seemingly irrelevant information may in fact be key to an investigation so we encourage everyone to let us be the judge. We would rather receive irrelevant information than miss something vital."
Mr Shephard was 1.7 metres tall with medium build and short blonde hair.
He was wearing a dark t-shirt and dark jeans. He may have been sitting somewhere along the track drinking with others or by himself.
Anyone with information is asked to contact Detective Sergeant Iain Chapman on 07 577 4374.